1. Field of the Invention
The present application relates generally to communications and networking. More particularly, the present application relates to multicasting in networks.
2. Description of the Background Art
Internet Protocol (IP) multicasting is an efficient technique for directing the same information packets to multiple receiving hosts. In comparison, unicasting sends a separate copy to each individual destination and is hence often much less efficient. Broadcasting differs from multicasting in that all hosts in a network receive and process broadcast traffic, while multicast traffic is, at least in theory, only received and processed by a controlled group of receivers.
Internet Group Management Protocol (IGMP) is a protocol of the Internet Protocol (IP) suite. IGMP may be utilized to control and limit the flow of multicast traffic through an IP network.
IGMP utilizes multicast “queriers” and hosts that support IGMP. A querier is a network device which transmits the queries and is typically a router. Queriers and IGMP hosts communicate with each other “query”, “report” and “leave group” messages. A query message is sent by a querier device to discover which network devices are members of a specified multicast group. A report message is sent by a host in response to a query to indicate a host's membership in the specified multicast group. A leave group message is sent by a host so as to remove itself from a multicast group.